The man -t is the crucial part. It tells man to produce output in postscript format, which ps2pdf can read, and evince displays the PDF. We disconnect the evince process using nohup, so that it lives on even if we kill the terminal. We `set -o pipefail` so that if `man` fails, the exit code is preserved as the exit of `man|ps2pdf`, which causes the `&&` to short-circuit, preventing evince from being run on an empty pdf document. We restore `+o pipefail` again at the end.